The Game of Logic

by Lewis Carroll

3. Some x exist.

4. All x are y'.

5. Some x are y. i.e. Some good riddles are hard.

6. All x are y. i.e. All good riddles are hard.

7. No x exist. i.e. No riddles are good.

8. No x are y. i.e. No good riddles are hard.

9. Some x are y'. i.e. Some lobsters are unselfish.

10. No x are y. i.e. No lobsters are selfish.

11. All x are y'. i.e. All lobsters are unselfish.

12. Some x are y, and some are y'. i.e. Some lobsters are selfish, and some are unselfish.